Thermostat



Feb. 19, 1935. n. MCK. GREER' THERMOSTAT Filed sept. 19, 1953 1 w l Z M, 7 6 Z Patented Feb. 19, -1935 UNITED STATES PATENT oEElcE THERMOSTAT David McKay Greer, Washington, D. C., assigner to American Instrument Company, Washington, D: C., a corporation of Delaware Application September 19,1933, Serial No. 690,151

7 Claims.

vide an'improvedA construction of mercury-in-y glass thermoregulator which may be more readily set at any desired operating temperature than any mercury-in-glass thermcregulator heretofore produced.

Another object of my invention is to provide a thermoregulator of such construction that the setting constant is reduced to zero.

Still another object of my invention is to provide a mercury-in-glass thermoregulator of improved construction such that setting the regulator may be accomplished in one sequence of operations as follows:

(l) -The lower (mercury-filled) bulb of the regulator is brought to the temperature at which the regulator is desired to operate by immersing it in a liquid or other medium at that temperature;

(2) The regulator is tipped until all the mercury in the upper bulb runs off into the side reservoir. o

A further object of my invention is to provide a mercury thermoregulator of improved construction such that all of the mercury above the upper electrical contact, at any temperature, may be removed from active participation in the operation of the regulator by simply tipping or tilting the regulator, without any change in the temperature of the regulator.

A still further object of my invention is to provide a construction of mercury-in-glass thermostat in which the bulb at the upper extremity of the capillary of the thermostat is provided with a chamber at one side thereof for receiving mercury expelled from the capillary by a tipping operation, or for restoring mercury to the capillary and effecting a setting operation.

Another object of my invention is to provide an improved construction cf thermostat including a bulb at the upper extremity thereof in which an auxiliary bulb extends from one side of the aforesaid bulb and provides a storage chamber for mercury for receiving vselected amounts of mercury from the bulb and for restoring the mercury to the bulb in effecting the setting ofthe thermostat.

Still another object of my invention is to provide a construction of thermostat having a capillary and a bulb at the upper extremity thereof with an auxiliary vessel connected to the bulb (Cl. ZOO- 141) through an intermediate plane or slightly concave area.

A further object of my invention is to provide a construction of thermostat having a capillary and a bulb at the upper extremity thereof with 5 an auxiliary vessel connected to the bulb with an intermediate upwardly projecting ,shoulder forming a lateral obstruction to prevent mercury from 'flowing from the bulb into the auxiliary vessel so long as the regulator remains in a vertical l0 or operatingposition.

A still further object of my invention is to provide a construction of mercury-in-glass thermostat which may be readily manufactured and in which the electrical connections from the termi- 15 nals of thepthermostat to the contacts in the capillary are formed by conductors wholly imbedded in the glass wall of the capillary.

Other and further objects of my invention reside in the construction of mercury-in-glass ther- 20 mostat as set forth more fully in the specification hereinafter following by reference to the accompanying drawing, in which:

Figure 1 is a side elevational view of the improved' thermostat of my invention partially 25 broken away and'illustrated in cross-section; Fig.

2 is a front elevational View of the thermostat illustrated in Fig.r1 in which the bulb of the thermostat is partially broken awayl and shown in cross section; Fig. 3 is a fragmentary cross sec-` 30 tional View of the upper portion of the thermostat l of my invention shown on a larger scale and illustrating the relation of the storage receptacle with respect to the bulb at the upper extremity of the capillary; Fig, 4 is a longitudinal cross- 35 sectional View through the upper portion of the thermostat taken on line 4-4 of Fig. 3; Fig. 5 is a lateral cross sectional View taken through the thermostat and storage receptacle on line 5-5 of Fig. 3; Fig. 6 shows the position of the mercury 40 in the bulb at the upper end of the capillary when the regulator has been brought up to a selected temperature; Fig. l schematically illustrates the manner of tipping the thermostat for removing all the mercury above the upper contact and effecting a setting operation; and Fig. 8 is a cross sectional View through the upper portion of a modified form of thermostat embodying my invention. y/

My invention is directed to an improved con-l struction of thermostat embodying the principles set forth more fully in my copending application Serial No. 663,843, filed March 3l, 1933 for Thermostats.

In my present construction of thermostat, 1.55

provide a capillary having a bulb at the upper extremity thereof with an auxiliary vessel connected eccentrically to the bulb. The auxiliary vessel forms a continuation of one side of the bulb and provides a reservoir for receiving mercury expelled from the capillary of the thermostat or delivering mercury for restoration to the capillary during the operation of setting the thermostat. The thermostat construction of my invention has no setting constant and the temperature at which the thermostat must work can be readily adjusted. That is to say, the quantity of mercury in the capillary may be readily changed. The thermostat may be set to operate at any selected temperature. Wherever I have referred to the setting constant of the mercuryln-glass thermoregulator in the specification, I refer to the number of degrees above operating temperature to which the mercury bulb would have to be raised before the necessary amount of mercury had been expelled from the capillary to permit the regulator to barely close contact when reduced to operating temperature.

In setting the thermostat, the main storage receplacle for the mercury is brought to the temperature at which the regulator is to operate. Surplus mercury above the capillary is then spilled over from the bulb intothe auxiliary vessel at one side of the bulb, leaving the column in the capillary barely making contact with the upper contact. This excess mercury is then no longer required and is retained in the auxiliary vessel. The thermostat is thus set to operate at a selected temperature and will continue to operate from time to time, as required. If it is necessary to re-set the thermostat for operation at a lower temperature, it is a simple matter to restore the excess mercury from the auxiliary ves,- sel to the bulb by tipping the thermostat, joining the mercury in the capillary to that in the bulb by heating the main storage receptacle, and then proceeding as before.

Referring to the drawing in detail, reference character 1 designates the capillary tube of the thermostat having a longitudinally extending bore 2 therein. The capillary is connected at its upper extremity with the bulb 3 and at its lower extremity with the main storage reservoir 14. The capillary tube has an electrical contact 6 in the form of a pin projecting radially through the wall of the capillary tube and into the bore 2 where connection is established with the body of mercury in the mercury column 12. A ring member 4 surrounds the capillary tube 1 and carries the contact pin 5 and provides an electrical connection for the conductor 6 for connecting the mercury column 12 to one side of an electric control circuit. It will be understood that the pin connector 5 may be located at any point along the mercury column 12 as the position of the contact pin 5 is not the temperature determining position but is merely the electrical connection which is established with the mercury column 12. The connection for the upper contact of the thermostat is completed by means of ring member 7 which embraces the capillary tube 1 and forms a terminal for the electrical conductor 8 for connection in the electrical control circuit of the thermostat.

A very special feature of my invention resides in the imbedding of the electrical conductor 9 wholly within the wall of the capillary tube 1 in the manner shown. One end of the conductor 9 is bent horizontally and extends radially outwardly. as shown at 9a and forms an electrical connection with the connecting ring '7. The upper end of the conductor 9 is bent horizontally, as indicated at 10, and is directed radially inwardly terminating in a contact 11 which is interiorly exposed at the bore 2 of the capillary at a position exactly at or very closely adjacent the junction of bulb 3 withthe upper end ofthe capillary tube 1. The bulb 3 is provided with an auxiliary vessel 16 connected at one side` thereof through a contracted neck l5. The auxiliary vessel 16 is blown from the Wall of the bulb 3 and depends in a position eccentric to the axis of the capillary 1. The auxiliary vessel 16 encloses a substantially smaller volume than the volume of the bulb 3. The connection between the auxiliary vessel 16 and the bulb 3 is constituted by a neck, smaller than the diameters of the bulb 3 and the auxiliary vessel 16 but of a size suilicient to allow the free transfer of mercury between the auxiliary vessel 1'6 and the bulb 3. The mercury which is stored within the auxiliary vessel 16 is shown at 17. In the form of the thermostat illustrated in Figs. 1-7, the upper end of the capillary 1 connects with the auxiliary vessel 16 along a curved surface which joins the bore 2 of the capillary 1 at a sharp peripheral edge indicated at 19. The horizontally extending shoulder 18 projects `up wardly from the curved surface and across the path between the capillary and the auxiliary vessel 16. Should the temperature over-run the regulator setting for any reason, the excess mercury which rises from the bore 2 of the capillary 1 rises above the peripheral edge 19 and along the curved surface and except for the location of shoulder 18 is in danger of being lost into the side reservoir or auxiliary vessel 16, which would change the subsequent operating temperature of the regulator. lThe shoulder 18 does not, however, prevent the transfer of mercury to reservoir 16 through neck 15 or obstruct the restoration of mercury to the bulb 3. In order to return the mercury in the bulb 3 to the capillary 1, the column in the capillary 1 must be joined with the mass in the bulb 3 by heating the lower bulb 14 until the column rises above the upper contact 11. Then the setting proceeds as before. No attempt is made to pour any regulated amount from the side reservoir back into the bulb, when returning mercury to the capillary. One simply returns more than enough, then pours olf the surplus when the proper temperature has been reached.

I may provide a modified construction of thermostat as illustrated in Fig. 8 in which a plane surface 20 interconnects the peripheral edge 19 with the auxiliary vessel 16 without the interposition of a limiting shoulder as illustrated in Figs. 1-7. In all forms of my invention the bore 2 extends without increase in diameter until it opens into the concave bottom of the upper bulb 3. In other words, the junction of the interior of bulb 3 with the bore of the capillary 1 is a relatively sharp peripheral edge.-

In order to facilitate the calibration and reading of the mercury column of the thermostat, I provide an opaque layer of material extending longitudinally of the bore 2 of the capillary 1, as represented in cross-section at 2l. This opaque layer forms a White background for the mercury column thus enabling the changes of the mercury column to be readily observed at all times without diiculty.

The auxiliary vessel 16, which is eccentric to the' main bulb 3, does not interfere with they normal operation of the thermostat and yet provides a storage chamber for the mercury at 17 which enables any to be transferred to desired quantity of mercury the bore 2 of the capillary l or removedy from the column 12 for storage into` of the thermostat at a predetermined temperature.

The ring member 'l is appliedto the capillaryv tube 1 in a position which will not interfere with the depending auxiliary vessel 16 and which is substantially in a plane extending through-the lower portion of the aux-'liary vessel 16. The fact that the conductor 9 is embedded in the wall of capillary tube 1 and extends from the contact 11 to the ring member 'l permits the electrical circuit to be terminated in a position adjacent the junction of the bulb 3 and the upper end of the capillary tube 1 while locating the ring member 'l well below the end of the capillary tube 1 in a position which does not interfere with the depending auxiliary vessel 16. At the same time, a high degree of permanency in the position and conductivity of the upper contact 11 isV assured by virtue of the imbedding of the conductor 9 in the wall of the capillary tube 1.

I have found the thermostat of my invention highly practical in its construction and while I have described the thermostat in certain of its preferred embodiments, I desire that it be understood that modifications may be made and that no limitations .upon my invention are intended -in a plane normal to other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows: 1. A thermostat comprising a capillary tube having a bulb on the upper and lower ends thereof, a bore extending through said tube and interconnecting said bulbs, a pair of electrical terminals having contact elements projecting into said bore,l and an auxiliary vessel formed integrally with the bulb at the upper end of said capillary tube ina position eccentric to the axis of the capillary tube, the upper end of said capillary tube intermediate said upper bulb and the opening to said auxiliary vessel, extending the axis of said capillary tube and providing a transfer path for mercury between the said bore and the said auxiliary vessel, said auxiliary vessel serving to store mercury transferred from said capillary tube or to replace mercury in the bore of said capillary tube for regulating the effective position of the mercury column in the bore of said capillary tube with respect to the electrical contacts therein.

2. A mercury and glass thermostatcomprising a capillary tube, a bulb at the upper and lower ends of said cap'llary tube; a bore extending through said capillary tube and interconnectlng the said bulbs, a mercury column in said bore, a pair of electrical contacts extending through said capillary tube and into the said bore, one of said contacts sealed in the wall of said capillary tube and being exposed in said bore at the upper extremity thereof, and an auxiliary vessel connected through a contracted .neck with one side of the bulb at the upper extremity of said capillary tubeand serving to store mercury transferred from the said bore preparatory to the retransfer thereof to said bore for adjusting the position of the mercury column with respect to said electrical contacts.

3. .A mercury and glass thermostat comprising a capillary tube, an

a capillary tube, a bulb at the upper an lower ends of said capillary tube, a borel extending through said capillary tube and interconnecting said bulbs, a mercury column in said bore, an electrical contact for establishing connection with the mercury column within said bore, a second electrical contact immediately adjacent the junction of the upper end of said capillary tube and the bulb at the upper end thereof, an electrical terminal mounted on said tube remote from said contact, a conductor extending longituvdinally through the wall of said capillary tube and connected with said latter contact at one end and connected with said terminal at the opposite end, an auxiliary vessel connected through a passage above the junction of the capillary and the upper bulb, and above the bottom of the auxiliary vessel, with the bulb at the upper end of said capillary tube and depending therefrom in a position adjacent said capillary tube and ending above said terminal, said auxiliary vessel serving to store mercury therein for transfer to said bore for adjusting the positionof the mercury column in said bore with respect to said electrical contacts.

-4.` A mercury and glass thermostat comprising expanding bulb filled with mercury and connected with the lower end of said tube, an overflow bulb connected with the upper end of said tube, a bore extending through 'said capillary tube and interconnecting said bulbs, an auxiliary bulb constituting a mercury reservoir bonnected with said upper bulb at the side thereof and depending therefrom adjacent said capillary tube, a mercury column in said bore, electrical terminals carried by said capillary tube, an electrical contact extending from one of said terminals directlyinto said bore, an electrical contact extending into said bore at the upper extremity thereof in a position remote from the other of said electrical terminals, and a conductor sealed into said capillary tube and extending longitudinally of said tubefor interconnecting said last mentioned electrical terminal and said last mentioned electrical contact.

5. A mercury and glass thermostat comprising a capillary tube, a bulb at .each end of said capillary tube, a bore extending through said capillary tube and interconnecting said bulbs, the lower of said bulbs constituting an expanding chamber, the upper of said bulbs constituting an overflow chamber, an auxiliary bulb constituting a mercury Areservoir connected with said upper bulb at theside thereof and depending therefrom in a position adjacent said capillary tube, an electrical terminal embracing said capillary tube and having an electrical contact extending therefrom through the wall of said capillary tube and into the said bore, a separate electrical terminal carried by said capillary 'tube and spaced substantially below the upper end thereof clear of said adjacent depending bulb, a contact extending into said bore at substantially the junction of said capillary tube with said upper bulb, a wire element interconnecting said last mentioned contact with said last mentioned electrical terminal, said wire element being wholly imbedded longitudinally in the wall of said capillary tube.

6. A precision mercury and glass thermostat comprising a mercury expansion bulb, a capillary terminating abruptly in an upper chamber,

and a side bulb opening oiI the upper chamber fio and formed integrally with it, a pair of electrical contacts, one of said contacts sealed into said capillary below the opening of the capillary into the upper chamber, and the other of said contacts sealed into the wall of said capillary above said first contact and entering said capillary at exactly the junction of capillary and upper chamber whereby the mercury column contacts said last mentioned contact at the limit of expansion of the mercury in said capillary.

7. A mercury and glass thermostat comprising a mercury expansion bulb, an upper chamber having a side bulb opening into it, a capillary connecting said expansion bulb and said upper chamber, electrical contacts sealed into said capillary, one of said contacts being exposed in said capillary exactly at the junction of said capillary and said upper chamber, said upper chamber and said side bulb being so disposed that all the mercury above the upper contact but none below it may be transferred into said side bulb by tilting said thermostat, the mercury in said side bulb remaining therein when said thermostat is righted, and so disposed also that mercury in said side bulb may be returned to the said upper chamber by tilting said thermostat in the opposite direction, mercury then in said upper chamber being insertable into the capillary by heating the expansion bulb until the mercury in the capillary joins that in the upper chamber, and subsequently cooling the mercury bulb.

DAVID McKAY GREER. 

